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scan.go
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scan.go
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package dbutil
import (
"database/sql"
"fmt"
"reflect"
)
func scanStruct(val reflect.Value, rows *sql.Rows) error {
meta := GetTableMeta(val.Type())
columns, err := rows.Columns()
if err != nil {
return err
}
if v, err := meta.GetScanFields(columns, val.Addr().Interface()); err == nil {
return rows.Scan(v...)
} else {
return err
}
}
func scanSlice(val reflect.Value, rows *sql.Rows) (interface{}, error) {
eleType := val.Type().Elem()
switch eleType.Kind() {
case reflect.Struct:
columns, err := rows.Columns()
if err != nil {
return nil, err
}
meta := GetTableMeta(eleType)
p, err := meta.PrepareScan(columns)
if err != nil {
return nil, err
}
for rows.Next() {
v := reflect.New(eleType)
fs, err := p.GetScanFields(v.Interface())
if err != nil {
return nil, err
}
if err := rows.Scan(fs...); err != nil {
return nil, err
}
val = reflect.Append(val, v.Elem())
}
default:
for rows.Next() {
v := reflect.New(eleType)
if err := rows.Scan(v.Interface()); err != nil {
return nil, err
}
val = reflect.Append(val, v.Elem())
}
}
return val.Interface(), nil
}
func scanRows(obj interface{}, rows *sql.Rows) error {
val := reflect.ValueOf(obj)
if val.Kind() != reflect.Ptr {
return fmt.Errorf("invalid scan type: %v", val.Type())
}
if val.IsNil() {
return fmt.Errorf("nil scan ptr")
}
objType := val.Elem().Type()
switch objType.Kind() {
case reflect.Struct:
if rows.Next() {
return scanStruct(val.Elem(), rows)
} else {
return sql.ErrNoRows
}
case reflect.Slice:
if s, err := scanSlice(val.Elem(), rows); err == nil {
val.Elem().Set(reflect.ValueOf(s))
return nil
} else {
return err
}
default:
if rows.Next() {
return rows.Scan(obj)
} else {
return sql.ErrNoRows
}
}
}
func Query(db *sql.DB, obj interface{}, q string, v ...interface{}) error {
if rows, err := db.Query(q, v...); err == nil {
defer rows.Close()
return scanRows(obj, rows)
} else {
return err
}
}